Memory leak (and other problems) with send_string() and recv_string()

[jwezel]

Both send_string() (alias send_unicode) and recv_string() (alias recv_unicode) leak memory. The following code reproduces the problem:

Server:

import zmq

cx = zmq.Context()
so = cx.socket(zmq.ROUTER)
so.bind('tcp://127.0.0.1:3333')
while True:
    p = so.recv()
    m = so.recv_unicode()

Client:

import zmq
import time

cx = zmq.Context()
so = cx.socket(zmq.DEALER)
so.connect('tcp://127.0.0.1:3333')
s = '**********************************************************'
for i in xrange(1000000):
    so.send_unicode(s)
    time.sleep(.001)
so.close()
cx.term()

Environment

• Python: 2.7.5
• pyzmq: 14.0.1
• zmq: 4.0.4

Furthermore, when the output queue fills up in the client (when sending too fast), then the error message
pyzmq-gc connect failed: Socket operation on non-socket is displayed which is not very helpful.

[minrk]

Anything that affects send/recv_string must also affect send/recv, unless there is a leak in the Python unicode.encode/bytes.decode methods (unlikely).

There is a leak in zero-copy send/recv in 14.0 (#486), which is fixed in master (by #517), but should only come up when copy=False. I bring this up because your comment about pyzmq-gc suggest that you are using zero-copy, where there is a known leak (fixed in master), but your sample here does not.

Can you reproduce the leak in current master?

[jwezel]

Nope, looks fine now. Thanks.

BTW, send_string/recv_string always do copy=False, shouldn't this be left to the caller of the method?

[minrk]

send_string does not set copy=False, but recv_string does. I'll fix that
now.​